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Hello,

Your max battery voltage is 45V and the max voltage on the LM2596 is 40V. Are you planning to have some voltage clamping at the battery so as to not exceed the device's max voltage?

1) The inductor values that are chosen are alright. For a buck regulator the inductor is chosen to provide a certain ripple current at the device's input/output voltages, and the switching frequency. In your case, the inductor will provide a 30% ripple current at the max input voltage of 45V. This also means that the ripple will be quite low at the min input voltage. I would suggest that you find the typiccal battery voltage and optimize the inductance value at that voltage to give you a 30% ripple current. The 30% is basically a number that gives an optimal sized ripple current. Since this is current mode control, the inductor ripple current is used to create the internal comparing ramp. If the ripple is very small (large inductance), then the proper functioning of the system can be compromised in case of bad SNR. If the ripple is too large (low inductance), then the output voltage can have too much ripple.

2) On both the devices, it would be helpful to add a small value ceramic bypass cap at the VIN pin. This helps provide for a shorter path for high frequency input current and this reduces noise in the system.

3) The devices you have chosen are some of our legacy devices. The switching frequency is very low and this causes the components to be oversized. If size is a concern, I would advise you to consider some of our newer devices such as the LM5576. If you are clamping the battery voltage to a certain voltage, then there are other even newer devices such as the LM43603 that can be used.

Hope this helps.

Regards,
Akshay

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